High-Pressure Die CASTING (HPDC) is one of the major production processes of the automotive industry, widely used to manufacture geometrically complex nonferrous CASTINGs. The mechanical strength and microstructure of HPDC-manufactured products change with variation in several process parameters such as injection pressure, molten temperature, 1st and 2nd stage plunger velocities, cooling temperature, etc. Since these process parameters directly a, ect CASTING quality, their optimum combination is needed to maximize productivity of the process and minimize CASTING defects such as porosity, pinholes, blowholes, etc. Hence, to tackle this problem, an approach is presented in this paper that minimizes the major CASTING defect, i. e., porosity, in the HPDC process by optimizing parameters through Design Of Experiments (DOE) in combination with Taguchi Analysis. The obtained results showed that cooling time, injection pressure, and 2nd stage plunger velocity had a major in uence on the response factor (density of the cast part). It was further concluded that by using a 178-bar injection pressure, 665, C molten temperature, 5 seconds of cooling time, 210 C mold temperature, 0. 20 m. s-1 1st stage plunger velocity, and 6. 0 m. s-1 2nd stage plunger velocity, the rejection rate of the selected part due to porosity was reduced by 61%.

Statement of Problem: Zirconia has been introduced as an appropriate structure for fabricating metal free copings. A major advantage of such restorations is esthetic concerns; however, due to its high strength, zirconia can also be used in posterior areas. One of the recent methods of making these restorations is CAD/CAM machines.Purpose: This study aimed to evaluate the fracture resistance of zirconia copings fabricated by two methods, CAD/CAM and slip CASTING.Materials and Method: 32 brass dies were fabricated for this study and divided into two groups of 16 dies each. Zirconia copings were made by CAD/CAM machine for one group and by slip CASTING method for the other. The copings were cemented to dies by a resin-modified glass ionomer (GC plus). A hardened steel ball with a diameter of 5 mm was used to apply the load to the copings in the long axis of the dies at a crosshead speed of 0.5 mm/min. Then the amount of force needed to fracture each coping was recorded. Independent Sample T-test was used to compare the two groups.Results: The average of fracture resistance for the CAD/CAM group was 1411±424 N and for the slip cast group it was 1542±412 N, having no significant difference (p>0.05).Conclusion: Zirconia copings made by CAD/CAM and slip CASTING methods have no significant difference in fracture resistance.

Background: There is no consensus in the treatment of de Quervain's tenosynovitis, but wrist support with or without local corticosteroid injection has been considered as an effective treatment modality. Some patients have expressed reluctance for steroid injections because of the fear of probable adverse reactions. This study was performed to compare the outcome of methylprednisolone acetate injection plus thumb spica cast versus cast alone for the treatment of de Quervain's tenosynovitis.Methods: This randomized prospective study was conducted from January 2005 to July 2008 in the orthopedic clinics of our hospital and private offices. A total of 73 patients with de Quervain's tenosynovitis were managed with either of these methods: 1) injection of methylpredmisolone acetate in the first dorsal compartment of the wrist followed by wrist thumb spica cast. 2) CASTING alone. Wrist CASTING duration in both groups was one month and the patients were followed for 6 months.Results: In the first group, a total of 37 patients were included (injection plus wrist immobilization by cast), and 36 patients in the second group (wrist CASTING alone). The mean age was 32.6 years (21-61 years) in all patients. There were 63 women and 10 men. Overall success rate was 86.5% in the first and 36.1% in the second groups, with a significant difference for both groups with respect to pain score and cure rate (P<0.05). Temporary pain was the most common adverse reaction at the site of injection and was noted in 40% of patients. Despite this adverse reaction which was related to methylprednisolone injection, a higher success rate was seen in the injection group in comparison to patients treated solely by CASTING.Conclusion: Support of the wrist with CASTING alone had less favorable outcome in de Quervain's tenosynovitis. Adding methylprednisolone acetate injection into the first dorsal compartment of the wrist is necessary for more optimal results.

During mold filling, molten metal can only advance as quickly as the air inside the cavity is expelled. In this work an analytical model describing air flow is developed based on a incompressible flow theory. Air pressure has serious effects upon the filling behaviour such as surface profile and filling time. In this work a new mathematical model is proposed for calculation the air pressure during the mold filling. A single phase computational fluid dynamic code based on the SOLA-VOF algorithm used for prediction the fluid flow. Air discharged through the vents is modelled by ideal gas assumption, conservation of mass equation and Bernoulli law. A new algorithm was developed to interpolates the air pressure on the surface cell. The creation of air back pressure was correlated with sizes of vents and pouring basin height. In order to verify the computational results a series of experimental test was conducted. Comparison between the experimental data and simulation results has shown a good agreement.

The present study is undertaken to calculate the rate of change of pressure and residual air mass in die CASTING for vacuum venting under choked flow conditions. In these calculations, the influence of friction factor, due to roughness and vent air velocity change through the Mach number, has been taken into account. The results show that there is a critical area ratio below which the pressure and vent inlet Mach number increase with time and above which decrease with time. In addition, for an area ratio less than the critical area, the rate of change of residual air mass seems to be more changed at the late stages than at the early stages of the filling time. The picture is reversed for a larger area ratio. This critical area ratio depends on vent area, filling time, evacuated volume, the initial pressure and temperature of the air in the die cavity.

Thin sheets of hydroxyapatite were fabricated by tape CASTING process. The non-aqueous tape CASTING formulation was optimized by adjusting the concentration of organic additives specially those of binder and plasticizer in the slurry. The optimized slurry was cast on a glass carrier using a designed laboratory scale doctor blade. Following a binder removal stage, the tapes were sintered at different temperatures in air atmosphere. Heat treatment at 1250 °C led to the formation of a dense microstructure as was evidenced by the scanning electron microscopy.

The concept of critical gate entry velocity was investigated in AZ91 magnesium alloy. The effect of in-gate velocity on the soundness and the mechanical properties of aluminum CASTINGs has been reported. Due to surface turbulence resulted by exceeding from the critical velocity and the entrainment of oxide film, mechanical properties and the performance of CASTING might be reduced significantly. Experimental work consisted of CASTING of plates, 10x140x200 mm of the AZ91 alloy in resin sand mold. The molten metal was introduced into the mold cavity at different gate velocities via changing the dimensions of a bottom gated filling system. Video recording was used to evaluate the possibility of the surface turbulence and the direct observation of the morphology of entrance of the melt jetted into the mold cavity at different velocities. Bend tests were carried out to investigate the effect of gate velocity on the mechanical properties of the CASTINGs in vertical and horizontal directions. Some results indicated that critical in-gate velocity for alloys is approximately 0.3m/s. Laminar fluid flow was observed at and below this velocity while at higher speed the morphology was changed into a mushroom shape and fountain shape of flow was noticed followed by about 50% decreased in the mechanical properties.